System for controlling ignition timing in an engine

ABSTRACT

A system for controlling ignition timing in an engine wherein a knocking signal is generated by a sensor in response to knocking. The operation of the sensor is monitored, and when a fault in its operation is detected, a dummy signal, instead of the knocking signal, is used to control engine timing. The dummy signal causes the engine timing to be retarded to a value at which knocking is unlikely to occur.

This is a division of application Ser. No. 42,343 filed May 25, 1979 nowU.S. Pat. No. 4,320,729.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a system for controlling ignitiontiming wherein knocking of an engine is detected, and ignition timing isinstantly delayed in response to the detected knocking. Moreparticularly, this invention is related to a system for controllingignition timing wherein, when a knocking sensor is out of order,ignition timing is delayed by a predetermined value.

2. Prior Art

Knocking of an engine is a dangerous phenomenon which may destroy theengine in the worst case. Hence, in the conventional ignition system,ignition timing is retarded from the ideal (with respect to performance)to ensure that knocking will not occur. However, since it is notdesirable from the viewpoint of economics of fuel consumption to delayignition timing simply to ensure knocking does not occur, a system hasbeen developed for controlling ignition timing wherein the occurrence ofknocking is fed back to advance the timing toward the ideal to thegreatest degree possible without the occurrence of knocking (forexample, Japanese Patent Application Laid-Open (Kokai) No. 87537/1977).

Now, in the system for controlling ignition timing as described above,knocking is detected to feedback control the ignition timing, theignition timing is delayed when knocking takes place, and the ignitiontiming is feedback controlled from engine conditions so as to advancethe ignition timing to the limits of knocking when knocking does notoccur. However, this system is disadvantageous in that, if a knockingsensor is out of order, the condition of knocking cannot be detected.Therefore the knocking sensor sends out a signal indication that noknocking exists despite the fact that knocking is occurring. Thus, theignition timing is unusually advanced to cause a violent knockingcondition in the engine. In the worst case this results in the meltingof the pistons and exhaust valves, which leads to the destruction of theengine.

SUMMARY OF THE INVENTION

One object of the present invention is to provide a system forcontrolling ignition timing wherein, when the knocking sensor is out oforder, the ignition timing is automatically controlled to apredetermined value irrespective of the presence or absence of thecondition of knocking, thereby preventing damage to the engine such asthe melting of pistons and/or valves.

In the present invention, ignition timing is controlled by an (ignitiontiming) advance control circuit for receiving the detected rotatingcondition of the engine and the presence of knocking detected by aknocking sensor. The degree of advance is controlled in proportion tothe rotating condition of said engine when no knocking takes place, andis delayed when knocking takes place.

The system includes a knocking sensor fault detecting circuit fordetecting a fault of the knocking sensor.

A dummy signal generating circuit generates a dummy signal to set theignition timing at a predetermined position on the delay side when saidknocking sensor fault detecting circuit detects a fault or constantlyirrespective of the presence of knocking signal.

An advance control signal controlling adjusts ignition timing inresponse to an output signal fed from said dummy signal generatingcircuit in place of a knocking signal when a fault of knocking sensor isdetected.

Thus, when the knocking sensor is normal, ignition timing is delayed bya knocking signal, and, when the knocking sensor is abnormal or out oforder, ignition timing is delayed by a preset dummy signal, to therebyachieve the aforesaid object.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram showing one embodiment of the system forcontrolling ignition timing of an engine according to the presentinvention;

FIG. 2 is a circuit diagram showing one embodiment of the system forcontrolling ignition timing by use of a circuit for detecting a fault ofthe knocking sensor and a circuit for detecting the engine load in anengine; and

FIG. 3 is a circuit diagram showing one embodiment of the system forcontrolling ignition timing of an engine wherein a fault of the knockingsensor is detected by use of a constant-voltage circuit.

DETAILED DESCRIPTION OF THE INVENTION

Detailed description will hereunder be given of the present inventionwith reference to the embodiments.

In FIG. 1, there is shown one embodiment of the system for controllingignition timing according to the present invention.

Referring to the drawing, a pulse rotor 1, provided at the marginalportion thereof with a required number of projections 1a, is rotated bya crankshaft of an engine as is well known, and is mounted in a mannerto be rotatable in the direction of advance by a centrifugal advancemechanism, vacuum advance mechanism or the like. Pickup 2 receivesignition pulses, which are applied to waveform shaping circuit 3. Saidpulse rotor 1, pickup 2 and shaping circuit 3 constitute an ignitionpulse detection circuit. Output pulses from the waveshape shapingcircuit 3 are adapted to be fed to an ignition timing calculationcircuit 5 and an updown counter 6 in a delay control circuit 4. Saidignition timing calculation circuit 5 generates a pulse in which theignition pulse fed from the waveshape shaping circuit 3 is delayed by avalue proportional to the output from the updown counter 6, and thearrangement of circuit thereof is well known, and hence, detaileddescription thereof will be omitted. Connected to the ignition timingcalculation circuit 5 is an output circuit 7 for sending out a delaypulse fed from the ignition timing calculation circuit 5 as an ignitionpulse. A knocking sensor 8 detects, for example, vibrations of the mainbody of the engine or sound waves caused by said vibrations andtransduces them into electric signals. Connected to said knocking sensor8 are a band pass filter 9 for allowing that portion of the outputsignal from said knocking sensor 8 within the knocking frequency band topass therethrough and a half-wave rectification circuit 11 in a faultdetecting circuit 10. Connected to said band pass filter 9 is a knockingdiscriminating circuit 13 for detecting signals fed from the band passfilter 9 which have a value larger in magnitude than a certain value andsending out a corresponding pulse to the updown counter 6 through aswitching circuit 12. Connected to said switching circuit 12 is a dummysignal generating circuit 17 for constantly sending out a signalidentical with the signal from knocking discriminating circuit 13 whenknocking is detected.

The fault detecting circuit 10 comprises the half-wave rectificationcircuit 11, an integration circuit 14, a comparison circuit 15 and anabnormality level setting circuit 16. Half-wave rectification circuit 11receives an output signal fed from the knocking sensor 8, half-waverectifies it and sends it out to an integration circuit 14. Integrationcircuit integrates the half-wave rectified signal and converts the sameinto a DC voltage value corresponding to the signal amplitude. Thesignal sent out by said integration circuit 14 is fed to a comparisoncircuit 15. Said comparison circuit 15 is of such an arrangement that itcompares an output signal fed from the integration circuit 14 with apreset voltage output signal fed from the abnormality level settingcircuit 16, and sends out an output signal when the output signal fedfrom the integration circuit is less in value than the voltage outputsignal fed from the abnormality level setting circuit 16. The outputsignal from said comparison circuit 15 is fed to the switching circuit12 connected thereto. The switching circuit 12 is of such an arrangementthat, upon receiving an input signal from the comparison circuit 15, theswitching circuit 12 discontinues to feed the signal from the knockingdiscriminating circuit 13 to the updown counter 6 and changes over tofeed the signal from the dummy signal generating circuit 17 to theupdown counter 6. When the signal from the comparison circuit 15 stops,the switching circuit 12 is restored to the initial condition, i.e. thecondition where the output signal from the knocking discriminatingcircuit 13 is fed to the updown counter 6. The updown counter 6 receivesa pulse fed from the shaping circuit 3 as a reference pulse in its downinput, and, receives a pulse fed from the knocking discriminatingcircuit 13 in its up input, and feeds a count output corresponding tothe difference between said two input pulses to the aforesaid ignitiontiming calculation circuit 5. In passing, the reference pulse fed to theupdown counter 6 is not limited to the pulse corresponding to therotation of the engine like the ignition impulse, but may be anoscillation pulse oscillating at a given cycle.

In said system for controlling ignition timing, when the engine isrotated, ignition pulses generated in the pickup 2 is converted to arectangular wave in the shaping circuit 3. A signal detected by theknocking sensor 8 is fed through the band pass filter 9 to the knockingdiscriminating circuit 13 which sends out one pulse per ignition cyclein which knocking occurs. When the ignition pulses are fed to the updowncounter 6 through the shaping circuit 3, said updown counter 6down-counts one count per pulse signal fed from the shaping circuit 3.Upon receiving a pulse signal from the knocking discriminating circuit13, said updown counter 6 up-counts one count. And, the ignition timingcalculation circuit 5 delays an ignition pulse fed from the shapingcircuit 3 in proportion to the value of stored in the updown counter 6.The delayed ignition pulse is fed to the output circuit 7 to therebydetermine ignition timing. The signal from the knocking sensor 8 is alsofed to the fault detecting circuit 10. The signal from the knockingsensor 8 is fed to the half-wave rectification circuit 11 of the faultdetecting circuit 10 to be half-wave rectified. A half-wave rectifiedpulse fed from the half-wave rectification circuit 11 is integrated bythe integration circuit 14, and converted into a DC voltage valuecorresponding to the signal amplitude. The DC voltage value thusconverted is fed to the comparison circuit 15, and compared with apreset voltage value in the abnormality deciding level setting circuit16.

When the voltage signal fed from the abnormality level setting circuit16 is larger in value than the voltage signal fed from the integratingcircuit 14, i.e. the knocking sensor 8 is out of order, a signal is sentout from the comparison circuit 15 to actuate the switching circuit 12.When the switching circuit is actuated, it discontinues to feed thesignal from the knocking discriminating circuit 13 and changes over tofeed the signal from the dummy signal generating circuit 17, whichconstantly sends out a signal identical with that of discriminatingcircuit 13 during knocking, to the updown counter 6. Additionally, whenno signal is received from the comparison circuit 15 to the switchingcircuit 12, the switching circuit 12 constantly feeds the output signalfrom the knocking discriminating circuit 13 to the updown counter 6.Upon receiving a signal from the dummy signal generating circuit 17, theupdown counter 6 is saturated to the maximum countable value which ispreset, and the ignition timing calculation circuit 4 feeds the maximumdelay value to the output circuit 7 to decide the ignition timing.

Consequently, the abnormality of the knocking sensor is discriminatedfrom the signal fed from the knocking sensor itself, whereby theignition timing is set at the predetermined position on the more delayside than the region of ordinary use when the knocking sensor is normal,thereby eliminated engine damage such as melting, losses of pistons, andthe like.

FIG. 2 shows another embodiment of the present invention.

In the drawing, the fault detecting circuit 10 is provided therein witha peak value holding circuit 23 in place of the half-wave rectificationcircuit 11 and integrating circuit 14 as shown in FIG. 1. Said peakvalue circuit 23 holds the peak value of the signal fed from theknocking sensor 8 and feeds the same to the comparison circuit 15. Saidcomparison circuit 15 compares the output signal fed from the peak valueholding circuit 23 with a preset signal fed from the abnormality levelsetting circuit 16, and feeds an output signal when the peak value ofthe output signal fed from the peak value holding circuit 23 is lowerthan the value of the output signal fed from the abnormality levelsetting circuit 16. The output signal from said comparison circuit 15 isfed to an "AND" circuit 21 connected to said comparison circuit 15.Connected to the "AND" circuit 21 is an engine load detecting means 20for detecting the engine load by a suitable method and sending out anoutput signal when the load is higher than the predetermined value. Said"AND" circuit 21 is adapted to feed an output to the switching circuit18 when "and" is achieved by an output signal from the comparisoncircuit 15 and an output signal from the engine load detecting means 20.Additionally, an output from the "AND" circuit 21 is fed to anindicating means 22, whereby abnormality of the knocking sensor 8 isindicated. Said switching circuit 18 is interposed between the ignitiontiming calculation circuit 5 in the delay control circuit 4 and theupdown counter 6, and is adapted, upon receiving an output from the"AND" circuit 21, to discontinue to feed the signal fed from the updowncounter 6 and change over to feed the digital signal fed from the dummysignal generating circuit 19 to the ignition timing calculation circuit5.

The signal fed from the knocking sensor 8 is converted to a DC voltagevalue by the peak value holding circuit 23, and compared with an outputvoltage fed from the abnormality level setting circuit 16, whereby thepresence of abnormality of the knocking sensor is decided likewise inthe embodiment shown in FIG. 1. More particularly, a voltage outputsignal fed from the peak value holding circuit 23 is compared with avoltage output signal fed from the abnormality level setting circuit 16connected to the comparison circuit 15 in said comparison circuit 15, itis decided that the knocking sensor 8 is out of order when the voltageoutput signal fed from the peak value holding circuit 23 is lower invalue than the voltage output signal fed from the abnormality levelsetting circuit 16, so that the comparison circuit 15 feeds a signal tothe "AND" circuit 21. On the other hand, when the engine load detectedby the suitable method is higher than the preset value, the engine loaddetecting means feeds a signal to the "AND" circuit 21. When "and" isachieved by the output signal fed from the comparison circuit 15 and theoutput signal fed from the engine load detecting means 20, the "AND"circuit 21 feeds a composite signal to the switching circuit 18. Uponreceiving the signal from the "AND" circuit 21, the switching circuit 18discontinues to feed the signal from the updown counter 6 and changesover to feed the digital signal from the dummy signal generating circuit19 to the ignition timing calculation circuit 5.

Consequently, in the present embodiment, a simple circuit can detect thepresence of abnormality of the knocking sensor, and moreover, even inthe case the knocking sensor is out of order, in order to eliminate theloss in the engine performance within the light load region which is notinvolved with knocking, the adoption of treatment based on the decisionof the presence of abnormality of the knocking sensor can beautomatically selected according to the load condition of the engine.Furthermore, it is avoided to shift said value to the delay side muchapart from the region of ordinary use for safety allowance. On thecontrary, said value is shifted to the delay side only slightly apartfrom the region of ordinary use. And, the operator may be warned of theabnormality in a separate way from the above.

FIG. 3 shows still another embodiment. The difference of this embodimentfrom the first embodiment shown in FIG. 1 resides in that an electricsignal load circuit 24 is inserted in place of the half-waverectification circuit 11 and the integrating circuit 14 in the faultdetecting circuit 10. Said electric signal load circuit 24 comprises aconstant-voltage circuit 25 and a resistance 26 which is seriallyinterposed between the constant-voltage circuit 25 and the knockingsensor 8. Said resistance 26 is connected at one side of theconstant-voltage circuit to the abnormality level setting circuit 16 andat the other side of the knocking sensor to the comparison circuit 15.

The fault of the knocking sensor 8 is detected in the following way. Ifan output voltage from the constant-voltage circuit 25 is applied to aninternal resistance 81 in the knocking sensor 8 through the resistance26, then a voltage value divided to the resistance 26 and the internalresistance 81 is generated in a knocking sensor signal wire 100. Saidvoltage value is fed to the comparison circuit 15 and compared with avoltage value fed from the abnormality level setting circuit 16 in thecomparison circuit 15. When the voltage value fed from the abnormalitylevel setting circuit 16 is lower than the divided voltage value fed tothe comparison circuit 15, it is decided that the knocking sensor 8 isout of order, an output is fed from the comparison circuit 15 of thefault detecting circuit 10 to the switching circuit 12, whereby theswitching circuit 12 is switched, so that an output signal from thedummy signal generating circuit 17 is fed to the updown counter 6.Others are the same as that described in FIG. 1.

Therefore, in the present embodiment, a specified electric signal is fedto the knocking sensor, and the abnormality of the knocking sensor maybe known from the condition of said electric signal being transmitted.

What is claimed is:
 1. A system for controlling ignition timing of anengine comprising:means for generating an operation signal related to anoperating condition of said engine; means for generating a knockingsignal related to knocking in said engine; means for controlling saidignition timing in response to said operation signal and said knockingsignal; means for determining a peak value of said knocking signal;means for generating a fault signal when said peak value is beyond apredetermined threshold; means for generating a dummy signal, said dummyhaving the effect of retarding said ignition timing to a timing at whichknocking is unlikely to occur when said dummy signal is applied to saidcontrolling means; and means for substituting said dummy signal for saidknocking signal to said controlling means in response to said faultsignal.
 2. A system for controlling ignition timing of an enginecomprising:means for generating first and second operation signalsrelated to first and second operating conditions of said engine; meansfor generating a knocking signal related to knocking in said engine;means for controlling said ignition timing in response to said firstoperation signal and said knocking signal; means for generating a faultsignal when said knocking signal generating means is inoperative; meansfor generating a dummy signal, said dummy having the effect of retardingsaid ignition timing to a timing at which knocking is unlikely to occurwhen said dummy signal is applied to said controlling means; gate means,responsive to said second operating signal and said fault signal, forgenerating a control signal when said second operation signal achieves apredetermined threshold and said fault signal is generated; and meansfor substituting said dummy signal for said knocking signal to saidcontrolling means in response to said control signal.
 3. A system as inclaim 2 wherein:said system further comprises means for determining apeak value of said knocking signal; and said fault signal generatingmeans includes means for generating said fault signal when said peakvalue is beyond a predetermined threshold.
 4. A system as in claim 2 or3 wherein:said first and second operation signal generating meansincludes means for detecting engine load, said second operation signalbeing an output of said load detecting means; and said gate meansgenerates said control signal when said second operating signalindicates a high load.
 5. A system for controlling ignition timing of anengine comprising:means for generating an operation signal related to anoperating condition of said engine; means for generating a load signalwhen a load on said engine is high; means for generating a knockingsignal related to knocking in said engine; means for controlling saidignition timing in response to said operation signal and said knockingsignal; means for determining a peak value of said knocking signal;means for generating a fault signal when said peak value is beyond apredetermined threshold, indicative of inoperativeness of said knockingsignal generating means; means for generating a dummy signal, said dummyhaving the effect of retarding said ignition timing to a timing at whichknocking is unlikely to occur when said dummy signal is applied to saidcontrolling means; an AND gate, responsive to said load signal and saidfault signal, for generating a control signal when said engine load ishigh and said knocking signal generating means is inoperative; and meansfor substituting said dummy signal for said knocking signal to saidcontrolling means in response to said control signal.
 6. A system as inclaim 1, 2 or 5 further comprising indicator means for informing anoperator when said dummy signal is applied to said controlling means. 7.A system for controlling ignition timing of an engine comprising:meansfor generating an operation signal related to an operating condition ofsaid engine; a knocking sensor having an internal resistance related toknocking in said engine; means for controlling said ignition timing inresponse to said operation signal and said knocking sensor; a resistanceconnected in series with said knocking sensor; means for applying avoltage across said knocking sensor and said resistance; means forgenerating a fault signal when a voltage between said knocking sensorand said resistance crosses a predetermined threshold indicative of saidknocking sensor being inoperative; means for generating a dummy signal,said dummy having the effect of retarding said ignition timing to atiming at which knocking is unlikely to occur when said dummy signal isapplied to said controlling means; and means for substituting said dummysignal for said knocking signal to said controlling means in response tosaid fault signal.
 8. A method of controlling ignition timing of anengine comprising the steps of:generating an operation signal related toan operating condition of said engine; generating a knocking signalrelated to knocking in said engine; controlling said ignition timing inresponse to said operation signal and said knocking signal; determininga peak value of said knocking signal; generating a fault signal whensaid peak value is beyond a predetermined threshold; generating a dummysignal, said dummy having the effect of retarding said ignition timingto a timing at which knocking is unlikely to occur when said controllingstep is responsive to said dummy signal; and substituting said dummysignal for said knocking signal in said controlling step in response tosaid fault signal.
 9. A method of controlling ignition timing of anengine comprising:generating first and second operation signals relatedto first and second operating conditions of said engine; generating aknocking signal related to knocking in said engine; controlling saidignition timing in response to said first operation signal and saidknocking signal; generating a fault signal when said knocking signalgenerating step is inoperative; generating a dummy signal, said dummyhaving the effect of retarding said ignition timing to a timing at whichknocking is unlikely to occur when said control step is responsive tosaid dummy signal; generating, in response to said second operatingsignal and said fault signal, a control signal when said secondoperation signal achieves a predetermined threshold and said faultsignal is generated; and substituting said dummy signal for saidknocking signal in said controlling step in response to said controlsignal.
 10. A method as in claim 9 wherein:said method further comprisesthe step of determining a peak value of said knocking signal; and saidfault signal generating step includes the step of generating said faultsignal when said peak value is beyond a predetermined threshold.
 11. Amethod as in claim 9 or 10 wherein:said first and second operationsignal generating step includes the step of detecting engine load, saidsecond operation signal being an indication of high engine load; andsaid control signal generating step generates said control signal whensaid second operating signal indicates a high load.
 12. A method ofcontrolling ignition timing of an engine comprising:generating anoperation signal related to an operating condition of said engine;generating a load signal when a load on said engine is high; generatinga knocking signal related to knocking in said engine; controlling saidignition timing in response to said operation signal and said knockingsignal; determining a peak value of said knocking signal; generating afault signal when said peak value is beyond a predetermined threshold,indicative of inoperativeness of said knocking signal generating step;generating a dummy signal, said dummy having the effect of retardingsaid ignition timing to a timing at which knocking is unlikely to occurwhen said controlling step is responsive to said dummy signal;generating, in response to said load signal and said fault signal, acontrol signal when said engine load is high and said knocking signalgenerating step is inoperative; and substituting said dummy signal forsaid knocking signal in said controlling step in response to saidcontrol signal.
 13. A method as in claim 8, 9 or 12, further comprisingthe step of informing an operator when said dummy signal is applied tosaid controlling means.
 14. A method of controlling ignition timing ofan engine comprising:generating an operation signal related to anoperating condition of said engine; generating a resistance related toknocking in said engine; controlling said ignition timing in response tosaid operation signal and said resistance; applying a voltage acrosssaid knocking related resistance and a known resistance; generating afault signal when a voltage between said knocking related resistance andsaid known resistance crosses a predetermined threshold indicative ofsaid resistance generating step being inoperative; generating a dummysignal, said dummy having the effect of retarding said ignition timingto a timing at which knocking is unlikely to occur when said controllingstep is responsive to said dummy signal; and substituting said dummysignal for said knocking signal in said controlling step in response tosaid fault signal.
 15. A system for controlling ignition timing in anengine, comprising ignition pulse emitting means for emitting anignition pulse in proportion to an engine rotating condition detected,knocking signal emitting means, including a knocking sensor, foremitting a knocking signal in response to knocking detected by saidknocking sensor, an updown counter for downcounting an ignition pulsefed from said ignition pulse emitting means and up-counting a knockingsignal pulse fed from said knocking signal emitting means, and anignition timing calculation circuit for sending out an ignition pulsefed from said ignition pulse emitting means after delaying it by a valuein proportion to a count value from said updown counter, wherein saidsystem further comprises:a knocking sensor fault detecting circuitincluding a peak value holding circuit for holding a peak value of saidknocking signal, an abnormality discriminating level setting circuit forgenerating a preset voltage signal, means for comparing said peak valuewith said preset voltage signal, wherein said knocking sensor faultdetecting circuit sends out a signal indicating a fault of the knockingsensor when said peak value is lower than said preset voltage signal;engine load detecting means for sending out a signal when an engine loaddetected is higher than a preset value; an "AND" circuit for taking alogical product between an output signal fed from said knocking sensorfault detecting circuit and an output signal fed from said engine loaddetecting means; a dummy signal generating circuit for generating adummy signal to set the ignition timing at a predetermined position onthe delay side; and a switching circuit for switching from an outputsignal fed from said updown counter to a dummy signal fed from saiddummy signal generating circuit and feeding the latter to said ignitiontiming calculation circuit in response to an output signal fed from said"AND" circuit.